The reaction of phenol and acetone over a catalyst to produce bisphenol A is known in the art. Catalysts which have been used include cation exchange resins and acids.
Generally, the use of acids represents the older method for the condensation of phenol with acetone. Representative acids include an aromatic sulfonic acid (German Offen 2,811,182 and U.S. Pat. No. 4,387,251), a volatile acid catalyst (U.S. Pat. No. 2,623,908), a strong mineral acid such as HC1 or H.sub.2 SO.sub.4 (U.S. Pat. No. 2,359,242), hydrochloric acid (U.S. Pat. No. 4,517,387), H.sub.2 SO.sub.4 or HC1 and 2-(4-pyridyl)ethanethiol (Japanese Kokai-57-118528), concentrated HC1 (Japanese Kokai 60-38335) and hydrogen chloride (U.S. Pat. No. 4,169,211).
Acidic mineral catalysts have several disadvantages. They necessitate construction materials which are considerably more expensive, they represent more of an environmental impact due to the cogeneration of waste materials and product purification is more costly.
A number of cation exchange resins have been used to convert phenol and acetone to bisphenol A. Representative catalysts are described in the following patents which are assigned to GE:
In U.S. Pat. No. 4,590,303, the cation exchange catalyst is a poly(styrene-divinylbenzene) copolymer which is partially modified by reacting the acidic groups with mercaptoalkylamines. Acetone conversions of 48-65% are observed.
In European Patent No. 144,735, the catalyst is a sulfonated polystyrene ion exchange resin having ionically bound (25-35 mol%) N-alkylamino-organomercaptan groups. Acetone conversions of 50-70% are observed.
U.S. Pat. No. 4,455,409 discloses an aromatic organic resin having amino-organomercaptan groups attached to 5-25% of the sulfonyl radicals by covalent nitrogen-sulfur linkages. Acetone conversion of 50% is observed.
U.S. Pat. No. 4,424,283 discloses a method for making leach resistant organoaminomercaptan substituted sulfonated aromatic organic polymers which demonstrate acetone conversions of 40-72%.
U.S. Pat. No.4,400,555 discloses a 2-mercaptoethylamine-modified, sulfonated, polystyrene divinylbenzene ion exchange resin situated in a series of reactors. Overall acetone conversion was 66%. In related U.S. Pat. No.4,391,997, the same catalyst is modified with mercaptoalkylamine.
A cation exchange catalyst comprising aromatic sulfonyl units substituted with an N-alkylamino-organomercapto radical was employed in U.S. Pat. No.4,396,728. In U.S. Pat. No.4,375,567 phenol was condensed with acetone over a sulfonated polystyrene ion exchange modified with mercaptan. U.S. Pat. No.4,365,099 discloses pretreatment of phenol with a chelating resin.
A number of patents assigned to Mitsubishi Chemicals also disclose resins for conversion of phenol and acetone to bisphenol A:
U.S. Pat. No.4,478,956 discloses a sulfonic acid type cation exchanger resin partially modified with a pyridine alkanethiol.
In Japanese Kokai 59-170031, a Diaion.RTM. SK-104 catalyst was added to a reactor as a suspension layer.
Japanese Kokai 57-85335 discloses the use of a sulfonic acid-type cation exchange resin partially modified with 2,2-bis[2-(4-pyridyl)ethylthio]propane where the phenol is pretreated with Diaion.RTM. SK-104.
In Japanese Kokai 57-72927, the resin is a sulfonic acid-type cation exchange resin modified with a mercaptan compound.
A different approach was taken in Japanese Kokai 61-78741, assigned to Mitsui Toatsu Chemicals using 5 parts of Lewatit.RTM. SC-102 and 10 parts of Molecular Sieve 5A.
In patents assigned to Shell, catalysts for bisphenol A reactions include sulfonic acid groups neutralized with an aminothiooarboxylio acid or ester or a thiazolidine compound (British 1,539,186), an acid ion exchange resin in the metal salt form modified with a mercaptan compound (U.S. Pat. No.4,191,843) and a cation exchange resin having sulfonic acid groups wherein amino thiophenol is used to bind directly to the aromatic nucleus (U.S. Pat. No.4,045,379).
The following references give an overview of catalysts which have been used to convert phenol and acetone to bisphenol A.
U.S. Pat. No.4,590,303--Poly(styrene-divinylbenzene) copolymers; PA0 ED 144,735--Sulfonated polystyrene ion exchange resin ionically bound with N-alkylamino-organomercaptan groups; PA0 U.S. Pat. No.4,455,409--Amino-organomercaptan groups attached to sulfonyl halides; PA0 U.S. Pat. No.4,424,283--Organoaminomercaptan substituted sulfonated aromatic organic polymers; PA0 U.S. Pat. No.4,391,997--2-Mercaptoethylamine modified sulfonated polystyrene divinyl benzene; PA0 U.S. Pat. No.4,396,728--A cation exchange catalyst comprising aromatic sulfony units substituted with an N-alkylamino-organomercapto radical; PA0 U.S. Pat. No.4,478,956--A sulfonic acid type cation exchange resin partially modified with a pyridine alkanethiol; PA0 Japanese Kokai 59-170031--A Diaion.RTM. SK-104 catalyst; PA0 Japanese Kokai 57-85335--A sulfonic acid-type cation exchange resin partially modified with 2,2-bis[2-4-pyridyl)ethylthio]propane; PA0 Japanese Kokai 57-72927--A sulfonic acid-type cation exchange resin modified with a mercapto compound; PA0 British 1,539,186--Sulfonic acid groups neutralized with an aminothiocarboxylic acid or a thiazolidine compound; PA0 U.S. Pat. No.4,191,843--An ion exchange resin in the metal salt form modified with a mercaptan compound; PA0 U.S. Pat. No.4,045,379--A cation exchange resin having sulfonic acid groups where amino thiophenol is used to bind directly to the aromatic nucleus.
The use of clays as catalysts for selected applications is known in the art. In an article titled "Catalysis: Selective Developments", Chem. Systems Report 84-3, 239-249, section 3.4320, the unusual properties of smectite clays which make them of interest as catalysts are discussed. These compositions are layered and exhibit a 2:1 relationship between tetrahedral and octahedral sites. In addition the combination of cation exchange, intercalation and the fact that the distance between the layers ca be adjusted provide interesting possibilities.
An article by F. Figueras, titled "Pillared Clays as Catalysts", in Catal. Rev.-Sci. Eng., 30, 457 (1988) discusses methods of modifying clays and the effects of the modifications. At page 472, there is a discussion of the method of drying, i.e. air drying or freeze drying, which can affect the macroporosity of the resulting product and, as expected, the adsorption capacity. The author concludes the thermal stability of pillared clays can be improved to reach 800.degree. C. using information available with respect to intercalation and drying methods.
Figueras notes, page 481, that the acid strength of montmorillonites wa found to be higher than that of Y-zeolites and, in the case of the clays, Bronsted acidity appears to be weaker than Lewis acidity. The author describes three kinds o acid sites known to exist at the surface of clay and suggests the coexistence of several types of acidity makes the localization of acid sites more difficult than in well-crystallized structures.
There are two reviews of the catalytic activity of pillared clays by T. Matsuda and E. Kikuchi, titled "Acidic Properties of Pillared Clays in Relation to Their Catalytic Behavior", in Proceedings of International Symposium on Acid-Base Catalysis, Sapporo, Nov. 28-Dec. 1, 1988. In Ch. 3.11 these
Catalyst authors observed Bronsted acid sites are responsible for isomerization whereas both Bronsted and Lewis acid sites can catalyze disproportionation. Other pertinent findings were that Bronsted sites are far more active than Lewis sites, however, studies would indicate an irreversible change of Bronsted acidity to Lewis acidity in the course of high temperature calcination, ibid, page 354. They concluded that cracking of a compound such as cumene, for example, depended only on the acidic properties, however disproportion activity was affected by the pore structure in addition to acidity. This was thought to relate to the fact that pillared montmorillonite had regular micropores while pillared saponite consisted of macropores. In addition saponite is tetrahedrally charged clay with Al cations substituting for Si cations. In montmorillonite, in contrast, Mg cations are octahedrally substituted for Al cations. At page 352, it is stated that cracking activity is satisfactorily related to Bronsted acidity while it is difficult to find any relationship between the disproportionation activity and the acidic property.
In British Patent GB 1,265,152 ortho-alkylated phenols were prepared in about 52% yield using Fulmont at 300.degree. C. with a small amount of sulfuric acid. In German Patent 2,552,175, KSF was the catalyst and about 15% para-product was formed.
There are two reviews of the use of pillared, cation-exchanged and acid-treated montmorillonite as catalysts for certain organic reactions by J. M. Adams et al., J. Inclusion Phenomena, 5, 663 (1987), Applied Clay Science, 2, 309 (1987). These clays display Bronsted and Lewis acid activities. It is noted that while some cationic species are stable in solution over a wide concentration and pH range, others are not, particularly solutions containing aluminum. It is noted that it is difficult to ensure a reproducible Al.sup.3+ clay and moreover, since workers have used slightly different exchanging and washing procedures, a comparison between related experiments is hindered. Commercial acid-treatment is carried out using concentrated hydrochloric, sulphuric or phosphoric acids. The concentration of the acid and the time of the treatment is variable. Sometimes the excess acid is removed by washing, whereas in other products this is not the case. Therefore there is a great variety in the type and activity of acid-treated clays.
Montmorillonites have been used as catalysts for the reaction of straight chain alk-1-enes to ethers, and for alkenes plus alcohols. In the latter, primary alcohols gave high yields, secondary less and tertiary alcohols only trace amounts. The Al.sup.+3 clays have efficiencies of one third to one half of Amberlyst.RTM. 15 in reactions of this type without solvent or using 1,4-dioxane.
The acid-treated clay K-306 can be used to convert methanol and ammonia to methylamines. Acid-treated clays have also been used to convert cumene hydroperoxide to phenol and acetone.
With respect to the production of bisphenol A most of the recent research and development has been concerned with BPA separation and purification. There is an increasing demand for high purity bisphenol A in polycarbonate resin manufacture. Catalyst enhancement is also of interest, see: "Bisphenol A and Alkylated Phenols," SRI PEP Report No. 192 (Dec. 1988) Section 4.
Processes using acid catalysts, such as anhydrous HC1, require extensive recovery facilities, product purification and waste treatment. In addition, the presence of highly corrosive streams requires the use of costly conversion-resistant construction materials.
The newer processes using a cation exchange resin catalyst have an advantage over the acid catalysts in that the resins are non-corrosive and require no catalyst recovery, Ibid, p. 5-1.
Though they represent an advance over the use of acid catalysts, the resins still have disadvantages. In a typical resin process design, the process unit is divided into three sections, condensation, separation and rearrangement and the operation of the condensation reactor is limited to &lt;120.degree. C. due to the low thermal stability of said resins. There is a necessity for extensive recycling of unreacted phenol/acetone, water removal, crystallization and purification.
It would be a distinct advance in the art if bisphenol A could be prepared in one unit using a more thermally and hydrolytically stable catalyst which did not require phenol/acetone recycling, pretreatment of the feed for water removal, etc. It would also be desirable if it did not use corrosive chemicals or require by-product salt handling an disposal. It would be particularly helpful commercially if the catalyst exhibited high thermal stability and extended catalyst life. Such a process would be especially attractive since it would be simpler to operate than processes currently used in the art.
It is an object of the instant invention to provide a one-step process for the synthesis of bisphenol A using a catalyst system which accomplishes the reaction in one step and exhibits extended life.